PHNOM PENH, Cambodia 
The Obama administration pressed Beijing on Thursday to accept a code of conduct for resolving territorial disputes in the resource-rich South China Sea, a difficult U.S. mediation effort that has faced resistance from the communist government - although it has endeared the U.S. to once-hostile countries in Southeast Asia.

U.S. Secretary of State Hillary Rodham Clinton met with Chinese Foreign Minister Yang Jiechi on the sidelines of the Association of Southeast Asian Nations' annual conference.

Sitting across from each other at a long table in a grand hall with chandeliers, Clinton stressed the different ways Washington and Beijing are cooperating. Yang spoke of building an even closer U.S.-Chinese relationship. Neither side spoke about the South China Sea while reporters were allowed in the room.

Several Asian governments have expressed worry about China's expansive maritime claims. Tensions have threatened to boil over in recent months, with a standoff between Chinese and Philippine ships and sharp disagreements between China and Vietnam.

China claims virtually the entire area and has created an entirely new city to administer it, sparking deep concern from rival claimants. The sea hosts about a third of the world's cargo traffic, has rich fishing grounds and is believed to store vast oil and gas reserves.

"The United States has no territorial claims there and we do not take sides in disputes about territorial or maritime boundaries," Clinton told foreign ministers gathered in Cambodia's capital. "But we do have an interest in freedom of navigation, the maintenance of peace and stability, respect for international law and unimpeded lawful commerce in the South China Sea."

Later Thursday, Clinton told delegates the U.S. was "intensely focused" on how countries were handling the different claims, singling out "confrontational behavior" in the disputed Scarborough Shoal off the northwestern Philippines, including the denial of access to other vessels. The actions she cited were China's, though she didn't mention the offending country by name.

According to Filipino officials, at different points earlier this year the Chinese attached fishing nets to ropes held by buoys to block entry to the sprawling lagoon at Scarborough Shoal, or tied several dinghies together with ropes. One official said the barriers were washed away by waves in recent storms. The officials spoke on condition of anonymity because the sensitivity of the issue.

"None of us can fail to be concerned by the increase in tensions, the uptick in confrontational rhetoric and disagreements over resource exploitation," Clinton said. "We have seen worrisome instances of economic coercion and the problematic use of military and government vessels in connection with disputes among fishermen. There have been a variety of national measures taken that create friction and further complicate efforts to resolve disputes."

ASEAN's 10 members announced earlier this week that they have drafted a set of rules governing maritime rights and navigation, and procedures for when governments disagree. But China is not a member of the group and hasn't agreed to anything.

The ASEAN countries are presenting their proposal to China at this week's conference in Cambodia's capital, though Beijing will probably want to water down any language that ties its hands.